Jordan Spieth, right, and caddie Michael Greller talk on the 16th tee during a practice round for the U.S. Open golf tournament in Pinehurst, N.C., Tuesday, June 10, 2014. The tournament starts Thursday. (AP Photo/Chuck Burton)

Jordan Spieth, right, and caddie Michael Greller talk on the 16th tee during a practice round for the U.S. Open golf tournament in Pinehurst, N.C., Tuesday, June 10, 2014. The tournament starts Thursday. (AP Photo/Chuck Burton)

Jordan Spieth, left, and caddie Michael Greller talk on the 14th hole during a practice round for the U.S. Open golf tournament in Pinehurst, N.C., Tuesday, June 10, 2014. The tournament starts Thursday. (AP Photo/Chuck Burton)

Justin Thomas hits out of a bunker on the 16th hole during a practice round for the U.S. Open golf tournament in Pinehurst, N.C., Tuesday, June 10, 2014. The tournament starts Thursday. (AP Photo/Charles Riedel)

Justin Thomas hits out of a fairway bunker on the 14th hole during a practice round for the U.S. Open golf tournament in Pinehurst, N.C., Tuesday, June 10, 2014. The tournament starts Thursday. (AP Photo/Chuck Burton)

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PINEHURST, N.C. (AP) â€” Michael Greller never imagined that a simple act of kindness eight years ago could lead to a moment like this at the U.S. Open.

Greller, the caddie for Jordan Spieth, stood on the 18th tee at Pinehurst No. 2 on Tuesday and conferred with his 20-year-old boss on an important tee shot in a match they didn’t want to lose against Phil Mickelson and Rickie Fowler.

Moments later, Greller was sharing a laugh with Spieth’s partner, 21-year-old Justin Thomas, who is playing in his first U.S. Open.

It was an amazing reunion among two players and one caddie â€” not because they were together, but the peculiar path that brought them here.

Thomas and Spieth have known each other since 2007, when they battled all summer on the junior circuit and were selected to represent the United States in the Evian Junior Masters in France. Thomas won the 36-hole event, and his reward was to play the Evian Masters pro-am with Juli Inkster. Spieth caddied for him.

They have been close friends ever since, and the needle in their playful banter is sharp.

And it’s that friendship that eventually took Greller from teaching math to sixth-graders to being the caddie for the No. 10 player in the world.

“Teaching 30 sixth-graders for 10 years prepared me for Jordan,” he said.

“Nothing can prepare you for Jordan,” Thomas replied.

Go back to the summer of 2006, a year before Spieth and Thomas even met.

Orchard Heights Elementary, on the west side of Puget Sound, had just let out for the summer when Greller went to Gold Mountain Golf Club to watch qualifying for the U.S. Amateur Public Links. He followed defending champion Clay Ogden, and in his group that day was Matt Savage, who was carrying his own bag.

“His buddy was supposed to caddie for him but at the last minute he couldn’t catch his flight,” Greller said. “That was the domino that started it all. I talked to his dad and said, ‘Hey, your son needs a caddie. I’ll work pro bono,’ thinking it would be one round. He was in 140th place.”

The next day, Savage rallied with a 69 to qualify for match play, and then he won three straight matches. The winner earned a spot in the Masters.

“I thought, ‘Wow, I’m three matches from Augusta,'” Greller said.

Savage lost his next match, and that was that. A new course called Chambers Bay opened the following year, and Greller transferred to a different school in the Seattle area so he could be a caddie in the summer.

The story could have â€” probably should have â€” ended there.

But four years later, Savage called Greller with a tip. Savage’s golf instructor in Louisville, club pro Mike Thomas, had a 17-year-old son who was headed to the U.S. Amateur at Chambers Bay and needed a caddie. That teenager was Justin Thomas.

“He thought I would be a good fit for Justin,” Greller said.

They hit it off and made it to the second round. Greller offered to fly to Wisconsin the following year to caddie for Thomas in the next U.S. Amateur.

Meanwhile, Spieth was headed to Gold Mountain for the U.S. Junior Amateur in 2011 and was in need of a caddie. Thomas recommended him to Greller, and Spieth wound up winning his second USGA title.

The next few years, Greller bounced between the two teenagers.

He worked for Spieth at the U.S. Open in 2012 at Olympic Club (Spieth was low amateur), and then headed to Cherry Hills to caddie for Thomas in the U.S. Amateur.

It wasn’t long before Greller’s career as a sixth-grade teacher ended.

Thomas was at Alabama. Spieth was starting his sophomore year at Texas when he decided to turn pro, and he asked Greller to be his full-time caddie. The first phone call Greller made was to Thomas, one of the toughest calls Greller ever had to make.

“I was at a basketball game,” Thomas said. “I talk to Michael a bunch but he doesn’t call me that often. We were catching up and then he goes, ‘Hey, man.’ And for some reason, it clicked. I said, ‘He’s gone.’ But I was so happy for him. It was a bummer not to have him, but I feel like I’m part of it, like I’m somewhere on that team and I’m cheering them on.”

Spieth went from no status on any tour in 2013 to a PGA Tour victory, the youngest American to play in the Presidents Cup and No. 7 in the FedEx Cup. Thomas left Alabama last year and already is No. 7 on the Web.com Tour money list, virtually assured of his PGA Tour card for next season.